1. Field of the Invention
This invention relates to therapeutic dentifrice formulations and in particular to dentifrice preparations comprising a soluble source of aluminum ions and a compatible dental abrasive material.
2. Description of the Prior Art
It is commonly recognized that the presence of small amounts of fluoride occurring naturally in drinking water (e.g., 1.0 microgram fluoride per milliliter) has a pronounced effect in reducing the incidence of dental caries in permanent teeth of children consuming such water from birth through eight years of age. Fluoride salts have been introduced into public water supplies in many communities with similar results. This method of dental caries prophylaxis is not available, however, to large numbers of people whose drinking water is obtained from small, private, fluoride-deficient sources such as individual wells and the like. Further, the addition of fluoride to common public water sources is not always accepted or permitted.
Topical application of aqueous fluoride solutions by dentists or dental hygienists likewise provide an excellent measure of protection against dental caries. Various fluoride compounds have been employed in this manner, including, stannous fluoride and sodium fluoride. Another method of employing the anticariogenic properties of fluoride salts comprises incorporating such materials with a compatible abrasive to form a prophylactic paste composition for use by dentists or dental hygienists on a professional basis.
Limitations on the availability of fluoride therapy by way of water supply or professional treatment has led to extensive efforts to incorporate fluoride salts in oral compositions for use in the home in the form of fluoride-containing dentifrices. Although effective dental caries protection has been obtained through the use of the aforementioned fluoride-containing compounds, occasional side effects have been experienced with certain of the known fluoride-containing anticariogenic agents, particularly certain tin-containing salts. For example, a brownish pigmentation of carious or precarious lesions has been experienced after anticariogenic agents containing the stannous ion have been applied to the teeth when the teeth are not properly cleaned with a toothbrush. Although the stain is not necessarily undesirable from a physiological standpoint, nevertheless, for esthetic reasons it would be desirable to provide an effective anticariogenic agent that does not pigment carious enamel.
The utility of certain of the prior art anticariogenic fluoride materials has also been limited by the extent of their solubility in aqueous media. For example, sodium fluoride is only soluble to the extent of about 4% in water.
Furthermore, because of the concern from a toxicity standpoint, current regulations imposed by the U.S. Food and Drug Administration limit the amount of fluoride that can be provided in products sold for over-the-counter use.
Finally, certain of the known prior art anticariogenic agents have been relatively unstable in aqueous solution. For example, stannous fluoride is subject to both oxidation and hydrolysis and for that reason must be used in freshly prepared form and must be used in conjunction with complexing anions in order to obtain its optimal anticariogenic effect.
As a result, dental researchers have continued the search for other anticariogenic agents to use in place of or in addition to fluoride-containing anticariogenic adjuvants. It has been suggested that aluminum salts may have a beneficial effect in reducing dental caries or in facilitating the uptake of fluoride by the dental enamel. See, e.g., Manly et al., "Substances Capable of Decreasing the Acid Solubility of Tooth Enamel", J. Dent. Res. 28; 160 (1948); Regolati, et al., "Effects of Aluminum and Fluoride on Caries, Fluorine Content and Dissolution of Rat Molars", Hev. Odont. Acta. 13: 59 (1969); and Kelada, "Electrochemical Characteristics of Free and Complexed Fluorides in Drinking Water and The Effects of Aluminum and Iron on Fluoride Incorporation Into Tooth Enamel," Univ. Michigan Thesis (1972).
In vitro studies have shown that pretreatment of enamel with aluminum solutions resulted in increased fluoride uptake when followed by treatment with a fluoride solution; however, treatment with combinations of aluminum and fluoride did not afford any added benefit over that of fluoride alone. McCann, "The Effect of Fluoride Complex Formation on Fluoride Uptake and Retention in Human Enamel", Archs. Oral Biol. 14:521 (1969); and Gerhardt, et al., "Fluoride Uptake in Natural Tooth Surfaces Pretreated with Aluminum Nitrate", J. Dent. Res. 51:870 (1972). Moreover, the foregoing techniques have dealt primarily wth the use of aluminum in combination with fluorides in acidic media and have not focussed on the effect of aluminum in the absence of fluoride and in alkaline media.
Thus, while some elements are known to inhibit dental caries (e.g., F, Mo, Sr, and V) and while others are known to promote dental caries (e.g., Se, Mg, and Cd), the preponderance of data on aluminum indicate that it is caries inert as classified by Navia, "Effect of Minerals on Dental Caries", in Dietary Chemicals vs. Dental Caries, A.C.S., Washington, D.C. (1970).
Nor has the use of aluminum salts in dentifrices demonstrated the desired result, primarily because it has not been recognized that conventional dentrifice constituents such as abrasives are incompatible with sources of biologically available aluminum. Thus, while French Pat. No. 3610M describes a specific combination of aluminum lactate, aluminum fluoride and calcium pyrophosphate, the abrasive interferes with the aluminum by reacting therewith to form insoluble aluminum phosphate. Similarly, U.S. Pat. No. 3,095,356 uses aluminum salts such as aluminum fluoride to coact with insoluble sodium metaphosphate abrasives to reduce the solubility of such abrasives and to increase fluoride uptake, but without independent therapeutic advantage being taken of the aluminum.
Canadian Pat. No. 829,272 describes acidic dentrifices comprising a combination of surface active substances and albumen coagulating substances such as certain carboxylic acid salts of aluminum and other metals. However, this patent likewise fails to teach that the satisfactory use of aluminum ions in dentrifices is dependent upon the use of aluminum-compatible constituents or that significant dental health benefits can be achieved with alkaline aluminum systems.
Thus, the prior art has not heretofore suggested a therapeutically effective aluminum system which provides biologically available aluminum as an anticariogenic oral composition.
Accordingly, it is a primary object of this invention to produce oral compositions incorporating a soluble source of aluminum ions and a compatible abrasive system which provides the aluminum ions to be presented in a therapeutically effective biologically available form in the oral cavity.
A related object of the present invention is to provide new and improved anticariogenic dentifrice preparations which need not contain fluoride ions.
A still further object of the present invention is to provide new and improved anticariogenic dentifrices.